The present invention is directed to a processor controlled or stored program telecommunications system similar to that shown by U.S. Pat. No. 4,339,633 issued July 13, 1982 and U.S. Pat. No. 4,379,950 issued Apr. 12, 1983 both to F. Ahmed. The system shown by the cited references is manufactured and sold by ITT Corporation under the name System 3100, and uses a two level control with a system controller common to the system and a plurality of group controllers, one per group of ports. Ports of the system may be standard single line station instruments, multi-line station instruments or trunks. In the system shown by the references, there are a number of features that are user programmable under the control of a remote, portable maintenance and diagnostic terminal, called a MAP panel. Note that the term user as applied in this specification refers to the sytem user or maintenance or supervisory personnel of the system owner or leaser to be distinguished from a port user of a station instrument or data terminal at a system port. With such a terminal, the status and class of service of ports of the system may be changed. Also in response to control from the panel, data from the system backup memory maintained on Electronically Alterable Read Only Memory (EAROM) can be loaded into the program memory which is stored in a random access memory (RAM).
The reference system is a processor-controlled, digital PBX/key system using eight bit PCM words for speech transmission, and asynchronous eight bit words for station control signalling on multi-line telephone instruments. The reference system has a maximum of one hundred and forty-four ports while using a one hundred and ninety-two time slot PCM speech bus for the system. Since there are more speech time slots available than ports, the system shown is in inherently non-blocking one. At the group level, there are twenty-four time slots per group and twenty-four ports.
Further, in the system shown by the references, a static RAM of 4k capacity is employed as the primary program memory within the system memory. Data concerning ports, features and class of service to be provided to specific ports may be changed in the program memory by the diagnositc terminal user. This data is also changed on the back up memory to place the back up and program memories in agreement. In the system shown by the references, the backup memory is EAROM and the method employed in placing the memories in agreement is to erase the entire EAROM memory and to restore the new data into from the backup memory.
Further, the system shown by the references stores its group controller work areas in RAM areas which are directly accessible from the MAP panel.